Roof tiles

ABSTRACT

A roof tile adapted for flat-packing includes on its under surface at least one region spaced from the or each hanging nib where the tile is deeper in cross-section than any other part of the tile. The underside of the or each region is configured so that when the tile is superposed on a second said tile, the tiles lie parallel and the underside lies in substantial contact with the upper surface of the second tile and prevents the hanging nib(s) of the first tile from contacting the upper surface of the second tile. By creating a region that is deeper than the depth at the hanging nibs, no load is borne by the nibs during stacking and the risk of the nibs breaking off during stacking and/or subsequent transportation is significantly reduced. In addition, because the tiles are specifically adapted to be flat-packed, the packs are particularly stable. A method of packing such roof tiles or other roof tiles of the cambered variety involves stacking layers of tiles on their side edges with the orientation of the tiles reversed in adjacent layers.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to roofing and cladding tiles having a substantially flat or cambered upper surface in use. For convenience, these tiles will be referred to hereinafter as flat roof tiles. The present invention also relates to a method of packing roof tiles, particularly cambered roof tiles.

[0002] Flat roof tiles generally have an upper edge, a lower (leading) edge which is visible in use when the tile is laid on a roof in overlapping relationship with at least one tile of a next adjacent line of tiles, an upper surface which is substantially planar or cambered, an under surface and two oppositely facing side edges. Frequently, the oppositely facing side edges are provided with complementary interlocking features in the form of an underlock which extends along one of the side edges and an overlock which extends along the other of the side edges. The under surface of the underlock forms part of the under surface of the tile and the upper surface of the overlock similarly forms part of the upper surface of the tile.

[0003] While the upper surface of such flat roof tiles is usually relatively featureless to provide the desired visual appearance (as opposed to profiled tiles which have an undulating or stepped upper surface), the under surface frequently includes a number of features which contribute to the overall technical performance of the tile. For example, the under surface usually has a hanging nib or a pair thereof located close to the upper edge for hanging the tile on a batten to which the tile is to be nailed when laid.

[0004] Additionally, the under surface may be provided with one or more strengthening ribs extending between the hanging nib(s) and the leading edge. Such strengthening ribs generally do not extend as far as the leading edge in order that they remain out of sight when the tile is laid on a roof and so do not spoil the leading edge appearance. Various arrangements of strengthening ribs may be found, for example they may run longitudinally, transversely or diagonally along the under surface or in any combination of these.

[0005] Further, in order to inhibit ingress of wind-driven rain, the under surface may be provided adjacent to the leading edge with a weather check located behind a channel which runs transversely between the side edges.

[0006] Such flat roof tiles may be made from a cementitious mixture such as concrete to resemble natural stone or slate, or from other materials such as clay. The most efficient way of making such tiles is by extrusion, rather than by pressing. An example of an extrusion process by which flat concrete roof tiles have been manufactured has been in use for over fifty years and involves charging a cementitious mix to a hopper-like box which is disposed above a conveyor on which a succession of pallets is conveyed. A rotating paddle in the box assists the flow of cementitious mix from the box to the pallets passing underneath. A rotating roller mounted within the box downstream of the paddle acts to compress the mix on the pallets. The roller is shaped to form the desired contour of the upper surface of the tiles whereas the pallets are shaped to mould the under surface of the tiles.

[0007] As the pallets are conveyed away from the box, the cementitious mixture is further compressed by means of a slipper disposed downstream of the roller. The slipper also has a shape that corresponds to the upper surface of the tiles. The resulting continuous extruded ribbon of mix on the pallets is subsequently cut into tile forming lengths downstream of the slipper by means of a cutting blade and optionally nail holes are punched in the tile forming lengths before they are conveyed to a curing location.

[0008] At the curing location, the tiles are initially held in a curing chamber maintained at a desired relative humidity and temperature for around six hours or longer and then the partially cured tiles are depalleted and stacked, usually out of doors, to complete the curing process. Once fully cured, the tiles are packed ready for dispatch to the customer.

[0009] Typically a small number of tiles, such as, say, four tiles, are stacked one on top of another before they are turned through 90° ready for loading, for example onto wooden shipping pallets. To facilitate handling, each stack may be secured by a flexible band or strap. Several such stacks of tiles, each tile now vertically oriented, may be loaded onto each pallet. In addition, each pallet load of tiles may be wrapped in a sheet material, such as polythene, to form a pack again allowing easier handling and providing a measure of protection to the tiles during transport. Each pack will generally comprise the same number of tiles which can range from say between three and fifty, although other pack sizes may be chosen as appropriate. Packs of tiles may be stacked on top of other packs during storage or transportation.

[0010] In an ideal packing arrangement, the tiles lie parallel to each other and, when stood end on, the top and bottom edges of the tiles combine to form a level “surface”. This is true flat-packing, allowing layers of tiles to be stacked economically and safely.

[0011] Unfortunately, reliable flat-packing is difficult to achieve and it is frequently the case that tiles become damaged during the packing process and/or subsequent transportation to the customer. To a great extent, the profile of the tile will determine how the tiles are most conveniently packed which in turn will dictate which part of the tile is most likely to be damaged. For example, the stacks may be turned so that the tiles stand vertically on either of their side edges, or on their upper or leading edges, or in combinations of these. However, each of these alternatives has its problems as will now be discussed below with reference to FIGS. 1a to 1 c and FIGS. 2 to 5 of the accompanying drawings. These drawings are in fact schematic diagrams illustrating flat roof tiles of known cross-sections that have been stacked prior to loading onto pallets.

[0012]FIG. 1a for example shows a stack of four identical tiles (2) each having on its under surface (4) a weather check (6) stretching between the side edges (8) adjacent its leading edge (10) and having a depth approximating to the depth of the hanging nib(s) (12). In theory, such a profile would appear to allow successful flat-packing of the tiles. However, in practice this is not achieved and damage to the hanging nib(s) (12) invariably occurs.

[0013] In particular, when the stack is turned through 90° (as shown in FIG. 1b) to a vertical orientation with the tiles' leading edges (10) lowermost, some slippage between the tiles (2) relative to each other often takes place. This slippage between the tiles (2) can easily result in the hanging nib(s) (12) getting caught over—or under if the tiles (2) are turned in the reverse direction to stand with their leading edges (10) uppermost—the upper edge (14) of an adjacent tile (2) in the group (as shown in FIG. 1c). Accordingly, the hanging nib(s) (12) of those tiles (2) that have slipped out of alignment with neighbouring tiles (2) in the pack are likely to be damaged, typically by breaking off, as they knock against the neighbouring tile edges (14).

[0014] Additionally, when one or more of the tiles (2) in a pack slip out of alignment as described above, what would otherwise be a level platform created by the aligned upper edges (14) of the tiles (2) becomes uneven. The result of this is that when another load of tiles (2′) is stacked on top of a base layer (as shown in FIG. 1c), those tiles (2) that have slipped out of alignment in the base layer end up as load-bearing elements for the layer above. The loads that the hanging nibs (12) are subjected to in this way may be considerable, further increasing the risk of the hanging nib(s) (12) breaking off.

[0015] Of course, even if the tiles (2,2′) shown in FIGS. 1a to 1 c were capable in practice of being flat-packed, the fact that leading edge (10) is at the same height as the hanging nib(s) (12) is a significant disadvantage, namely because the leading edge (10) is somewhat thicker than that considered to be visually acceptable.

[0016] Instead of providing a weather check (6) adjacent the leading edge (10) as in the tiles (2, 2′) of FIGS. 1a to 1 c, another option that has been considered is to provide the under surface (4) with one or more packing lugs (16) positioned away from the leading edge (10) (as shown in FIG. 2). While these packing lugs (16) are of a similar depth to that of the leading edge (10) in FIGS. 1a to 1 c, their positioning on the tile (2) is such that they are not visible when the tile (2) is laid on a roof and the tile (2) can be formed with a relatively thin leading edge (10) which is visually more pleasing.

[0017] While the design of tiles shown in FIG. 2 therefore overcomes the aesthetic disadvantages of the tiles of FIGS. 1a to 1 c, in practice the problems of the tiles slipping as they are turned through 90° to the vertical remain. In other words, there is still the opportunity for the hanging nib(s) to get caught over the tipper edges of adjacent tiles and therefore still a high risk of damage to the hanging nib(s). Accordingly, these tiles are also incapable of being reliably flat-packed.

[0018] One way of overcoming the problems caused by relative movement between the tiles when the tiles are turned to be vertical is by providing the upper surface of each tile with one or more depressions sufficiently deep to accommodate the or each hanging nib of an adjacent tile in the stack. A stack of such tiles is illustrated in FIG. 3. It will be appreciated that when such a stack is turned through 90° so that the tiles (2) have their leading edges (10) lowermost, there is no opportunity for any one of the intermediate tiles (2) to slip down because each tile (2) has its hanging nib(s) (12) nesting in the depression (18) of an adjacent tile (2). And even if an end tile (2) slips down, as it is brought to rest on an underlying support surface—such as a pallet—the adjacent tile(s) (2) are free to drop to the same level.

[0019] While this particular tile design allows for true flat-packing, an additional processing operation is required in order to create a depression in each tile. This is not too much of a problem in relation to pressed tiles, such as clay tiles, where the depression is created simply by pressing into the wet clay on that part of the upper surface which corresponds to the position of the hanging nib(s) on the under surface. However, in the more “streamlined” extrusion process where the tiles are formed from a continuous ribbon of concrete with the roller and/or slipper creating a continuous and uniform upper surface, the depression must be created by scooping out some of the wet concrete from each of the tile forming lengths. Apart from slowing down production, it will be appreciated that the potential for equipment failure and/or manufacturing irregularities is increased by the inclusion of this additional step and consequently the risk of wastage is increased.

[0020] In any event, removing material to create one or more depressions or recesses in the upper surface in the region of the hanging nib(s) may result in the tile becoming structurally weak in that region. Consequently, any mishandling of the tile might result in damage thereby rendering the tile useless. For this and the aforementioned reasons, the tile design as shown in FIG. 3 is less than ideal.

[0021] Other ways of stacking the tiles to achieve flat-packing have been proposed. For example, one means for obviating the need for suitable recesses in the upper surface of extruded tiles, or for avoiding the need to provide a thick leading edge or packing lugs, is to reverse the orientation of adjacent tiles in a stack and off-set them relative to each other. This will usually mean that every tile, apart from the end tile, in the stack has the hanging nib(s) of an adjacent tile resting against its upper surface bordering its leading edge. FIG. 4 illustrates such an arrangement.

[0022] By alternating the orientation of the tiles (2) in this way, there is a risk of the upper surface (20) adjacent the leading edge (10) becoming scuffed or scratched by the hanging nibs (12). This damage may be caused during stacking or unpacking if particular care is not taken to avoid scraping the hanging nib(s) (12) against the upper surface (20) of an underlying tile. However it is caused, any damage in the vicinity of the leading edge (10) will detract from the appearance of the tile and result in it being of unacceptable quality for laying on a roof.

[0023] Aside from the above, while the tiles (2) of FIG. 4 benefit from a thin leading edge (10) without any packing lugs and are less likely to slip relative to each other when the stack is turned through 90°, the hanging nib(s) (12) of the tiles (2) would remain load bearing elements if they were loaded on pallets with their side edges vertical. However, it is more usual for such a stack to be turned so that the upper (14) and leading edges (10) of the tiles are vertical. In this way, instead of the hanging nib(s) (12) being load bearing, the interlocks (not shown) formed along the side edges (8) become the load bearers. As the underlock and overlock are generally the thinnest parts of the tile (2), they are even more prone to damage than the hanging nib(s) (12) when placed under load. This arrangement does not therefore present a practical solution to the packing problem.

[0024] Whichever way the tiles are stood, altering the orientation of successive tiles in a stack is not particularly convenient, as the packing process is inevitably slower than when keeping all the tiles in the same orientation. Furthermore, there is also the inconvenience of presenting a tile layer with a stack of tiles in which the orientation of successive tiles is reversed. Although the latter aspect is not a massive problem for the tile layer, and he may well find it irritating and cause him to be less efficient, it is certainly disadvantageous to have to pack the tiles in this manner.

[0025] Another possibility would therefore be to group the tiles in pairs and alter the orientation of adjacent pairs of tiles in a stack as shown in FIG. 5. In this way, when an even number of tiles (2) is stacked they still form a level pack. However, this is not really any less inconvenient than altering the orientation of every successive tile (2).

[0026] Moreover, this is not true flat-packing because the tiles (2) are not parallel to each other and, when turned on end, their top and bottom edges (10, 14) do not combine to form a level surface even if the stack were to remain intact. Of course, as with the arrangements shown in FIGS. 1a to 1 b and FIG. 2, such a stack of tiles (2) is unlikely to remain coherent. Rather the tiles (2) are liable to slip out of alignment with each other in a similar way to that shown in FIG. 1c. Consequently, this arrangement too suffers from the problem of the hanging nib(s) (12) becoming load bearers.

[0027] Accordingly, there remains a need for a flat roof tile that is amenable to flat-packing and in which the aforementioned disadvantages are eliminated or at least substantially reduced.

SUMMARY OF THE INVENTION

[0028] From a first aspect, the invention resides in a flat roof tile comprising an upper edge, a lower edge, two oppositely facing side edges, an upper surface and an under surface provided with at least one hanging nib, wherein the under surface includes at least one region spaced from the or each hanging nib where the tile is deeper than any other part of the tile and the underside of the or each region is configured so that when the tile is superposed on a second said tile, the tiles are parallel and the underside lies in substantial contact with the upper surface of the second tile to prevent the hanging nib(s) from contacting the upper surface of the second tile.

[0029] By virtue of creating a region deeper than any other part of the tile, including the depth at the hanging nib(s), and configuring its underside in the manner described, the ability to flat-pack said tiles without having to turn alternate tiles and without having to stack the tiles in an off-set relationship can be successfully and safely achieved.

[0030] More especially, because the depth at the hanging nib(s) no longer constitutes the deepest part of the tile, when the tiles are superposed to form a stack, the nib(s) are spaced from the upper surface of an adjacent tile and are substantially prevented from getting caught over the upper edges of adjacent tiles in the event that any tiles slide relative to each other when they are turned to stand end-on. In other words, no load is borne by the hanging nibs and the risk of damaging the nibs during stacking or once packed is significantly lessened.

[0031] Of course, since the underside of the region of deepest cross-section is in substantial contact with the upper surface of an adjacent tile, to an extent the tiles are inhibited from sliding relative to each other. A yet further advantage of creating substantial contact in this way is that the packed tiles are substantially prevented from “rocking” relative to each other which feature also contributes to lessening the risk of damage to the visible upper surface or to the leading edge. Not only therefore are the tiles according to the invention able to be flat-packed successfully, but the resulting pack is highly stable.

[0032] The above advantages are achieved simply by going against conventional wisdom which has pointed towards making the hanging nib(s) the deepest part of the tile or at least deep enough to rest on a supporting surface when the tile is laid flat or on an underlying tile when the tile is stacked with other like tiles. The Applicant has surprisingly found that it is not necessary for the hanging nib(s) to project so far for the tile to meet all relevant functional requirements.

[0033] For the avoidance of doubt, references to the depth of the tile are to be construed as the overall depth of the tile when viewed in cross-section, in other words the depth is measured from the upper surface.

[0034] In a preferred embodiment, the underside of the region of deepest cross-section has a contour that is complementary to the contour of upper surface above the region. In this way, when the tile is superposed on another such tile during the packing process, the underside of the region of one tile is substantially in contact with the upper surface of the other tile across the whole of the region. By increasing the area of contact between the underside and the upper surface of adjacent tiles, stability of the pack is further enhanced.

[0035] Moreover, having the complementary contours neatly avoids any point-contact between adjacent tiles and helps to spread the load exerted by adjacent tiles more widely. This may be of benefit in reducing the opportunity for damage to the visible part of the upper surface during packing and once packed.

[0036] When the upper surface of the tile is substantially planar to provide a truly flat tile, the aforementioned region desirably has a planar underside. On the other hand, when the upper surface is cambered, the underside of the region is ideally concave with a degree of curvature complementary to the camber. However, the underside of the region does not have to be continuous, for example, it may comprise a series of ridges or projections, the lowest points of which when viewed together, form the desired contoured region under surface.

[0037] Preferably the region of deepest cross-section is such that it is only marginally deeper than the maximum depth at the hanging nib(s). In this regard, the depth of the tile at the region need only be just sufficient to avoid frictional contact between the hanging nib(s) and the upper surface of another such tile when the tiles are superposed. For example, the depth at the region may be as little as 0.1 mm greater than at the hanging nib(s). In this way, the amount of material required to provide the region is kept to a minimum. Preferably, the tile is about 0.5 mm deeper at the region than the depth at the hanging nib(s).

[0038] It is also preferred that the region of deepest cross-section be configured so as not to interfere with an underlying tile in an adjacent row when the tiles are laid on a roof. This may be achieved by ensuring that the region of deepest cross-section does not extend into the area of the under surface that overlaps in use with the upper surface of an underlying tile in an adjacent row. To ensure a measure of flexibility in the spacing between adjacent rows of tiles, the region of deepest cross-section ideally should not extend into the overlap area created when the tiles are laid at maximum headlap.

[0039] Equally, to avoid any alteration of the angle at which the tile would otherwise hang on the roof, the region of deepest cross-section should preferably not extend into the area of the under surface that rests in use against a roof batten.

[0040] To ensure that the tiles are well balanced or stable, and the load distributed almost uniformly across the tiles when stacked vertically, the region of deepest cross-section preferably encompasses the middle portion of the tile, that is, spaced inwards from both the upper and lower edges and the opposing side edges. Where more than one such region is provided, these are also preferably spaced inwards from each of the four edges. Ideally the or each region is located centrally of the tile's contact points with the roof when the tile is laid. These contact points generally comprise the hanging nib(s) at one end and the weather-check at the other. Expressed in another way, the or each region is ideally located symmetrically around the mid-point of the unsupported tile span in use. For optimum balancing and load distribution, the underside of the region of deepest cross-section extends for between about one third to two thirds of the length or width of the tile or both.

[0041] To optimise the strength to weight ratio of the tile, the under surface of the tile is preferably tapered so that there is a gradual reduction in depth away from the region of deepest cross-section.

[0042] In a particularly preferred embodiment, the tile is provided on its under surface with a pair of spaced apart ribs, such as strengthening ribs, wherein each rib includes along a mid-portion a region having the aforementioned depth and contact characteristics as required by the invention. Of course, a single such rib, most preferably centrally placed on the under surface of the tile, would suffice, but having a pair of such ribs spaced apart provides for improved strength and offers greater benefits in terms of stability when the tiles are stacked in a pack. The region of deepest cross-section ideally occupies the central portion of the rib, and more preferably extends for between about one third to two thirds of the total length of the tile. The remainder of the rib may taper gradually along its length towards the outer edges of the tile, but stopping short of the edges in order that it remains out of sight when the tile is laid on a roof.

[0043] From another aspect, the invention resides in a roof tile having a substantially planar upper surface and an under surface from which one or more hanging nibs depend, characterised in that the under surface is provided with one or more elongate ribs each having a median portion that depends beyond the depth of the hanging nib(s) and its underside is of complementary configuration to the upper surface lying immediately thereabove.

[0044] Ideally, a pair of strengthening ribs having the required characteristics are symmetrically disposed on either side of the mid-point of the under surface of the tile. Moreover, while such strengthening ribs may extend transversely or diagonally along the under surface, it is most preferred that the ribs extend longitudinally between the upper edge and lower edge. Also, it is a preferred arrangement for the ribs to be spaced substantially equidistant from each other and from the side edges of the tile such that the under surface is effectively divided into thirds by the ribs.

[0045] By contrast to the strengthening ribs found in the tiles of the prior art, such ribs will include the deepest part in cross-section of the tile, rather than the hanging nib(s). As will be appreciated, making the strengthening ribs even thicker in this way not only provides the aforementioned advantages in allowing successful, stable flat-packing, but may also improve the overall strength of the tile.

[0046] Another advantage of increasing the depth of tile in the specified region(s) to a depth greater than the hanging nib(s) is that it enables the dimensions of the tile to be increased without requiring the whole tile to be thicker. This can be achieved without unduly sacrificing tile strength. This is particularly important as a tile that is thicker overall will tend to have a thicker leading (lower) edge that is less attractive from an aesthetics point of view. The present invention therefore makes it possible to enlarge the footprint of the tile without enlarging the thickness of the leading edge, yet at the same time maintain adequate strength.

[0047] By way of example, the Applicant currently manufactures a flat concrete tile having the dimensions 330 mm×265 mm. By means of the present invention, namely by changing the relative depths of the hanging nibs and strengthening ribs, so that the strengthening ribs include the regions of deepest cross-section, the Applicant has been able to extend considerably the length of the tile yet still achieve a tile strength that compares favourably with their existing tile. One such enlarged tile produced in accordance with the invention has the dimensions 334 mm×420 mm, representing an increase in surface area of almost 40 percent. Hence there are also cost benefits associated with the present invention in that it enables larger tiles to be made resulting in less tiles per square metre being laid on the finished roof.

[0048] Optionally, the tiles according to the invention may be provided with means to restrain the tiles from rocking relative to each other when the tiles are stacked. For example, when a mid-section of one or more strengthening ribs provides the region of deepest cross-section and the rib(s) is/are located nearer to the centre of the tile as opposed to the side edges, there is a possibility that the tiles might rock slightly if pressure is applied near a side edge of an uppermost tile in the stack. To this end, anti-rock means may be located on the under surface of the tile adjacent both side edges. Preferably, the anti-rock means comprises a pair of protuberances, each projecting from the under surface adjacent opposite side edges and being substantially centrally positioned along the length of the tile. These protuberances may project from additional strengthening ribs running alongside the side edges. However, while the protuberances should project sufficiently to substantially inhibit any rocking between adjacent tiles in a stack, such anti-rock means do not generally comprise the deepest part of the tile.

[0049] While the invention is not limited to tiles made according to a particular method, for example they may be manufactured by pressing or by extrusion, the latter method lends itself particularly well to these tiles and is therefore the preferred manufacturing method. Moreover, the invention is most preferably directed towards concrete tiles, especially concrete roofing tiles.

[0050] The invention also resides in an array of tiles as hereinbefore described for use on a roof and to a roof construction comprising an array of tiles as hereinbefore described laid in successive rows on and affixed to a roof surface. The invention further encompasses a ventilation tile adapted to be interposed between and interlock with the tiles as hereinbefore described in a roof construction. Such a ventilation tile preferably has the same overall dimensions as the roofing tile and the same underlock and overlock features.

[0051] While the tiles according to the invention lend themselves especially well to being stacked vertically, for example, so that their leading edges rest against a pallet and their upper edges combine to form a level surface on which a further layer or layers of tiles can be stacked, other stacking arrangements are possible.

[0052] To this end, the Applicant has discovered a particularly advantageous way of stacking cambered roof tiles to form a stable pack. The stacking method is applicable not only to cambered roof tiles made in accordance with the principles of the present invention, but also to cambered roof tiles in general. It is particularly applicable to interlocking cambered roof tiles, namely those tiles that are provided along their respective side edges with underlocks and overlooks.

[0053] Accordingly, from another aspect, the invention resides in a method of forming a pack of cambered roof tiles, the method including stacking together a first group of said tiles so that each tile in the group is supported on a side edge with their respective upper and lower edges parallel and vertically aligned to form a first layer of said tiles, stacking together a second group of said tiles on top of said first group, the tiles in said second group also supported on a side edge with their respective upper and lower edges being parallel and vertically aligned to form a second layer of said tiles, wherein prior to stacking on the first group, the tiles of the second group are turned through 180° to face the opposite direction to those of the first group.

[0054] Expressed in another way, the invention further resides in a pack of cambered roof tiles comprising first and second layers of tiles, the tiles in each layer stacked together and supported on their side edges with their respective upper and lower edges parallel and vertically aligned, wherein the orientation of the tiles in the second layer is reversed such that they face the opposite direction to the tiles of the first layer.

[0055] The expression “stacking together” means that the upper surface of one tile abuts against the under surface of an adjacent tile. In the case of the tiles previously described in accordance with a first aspect of the invention, the underside of the or each region of deepest cross-section on one tile would lie in substantial contact with the upper surface of an adjacent tile when stacked together.

[0056] As will be appreciated, even when the tiles are stacked together, there will be spaces between adjacent tiles where they do not abut. This is especially so in the region of the interlocks which, by their very nature, are thinner in cross-section than the main body of the tile. By simply reversing the orientation of the tiles in adjacent layers, the Applicant has discovered that it is possible substantially to prevent a tile in an upper layer from slipping down between adjacent tiles in the layer below. This is because the direction of the camber is reversed in adjacent layers effectively “narrowing” the gap available between abutting tiles for the oppositely curved side edge (usually the interlock) of an overlying tile to fall into to such an extent that it cannot be accommodated.

[0057] By means of this further invention, the potential for damaging the side edges, particularly the interlocks, caused through slippage between layers can be significantly reduced. Previously, the use of sheet material interposed between adjacent layers has been desirable to prevent such slippage, but this aspect of the invention renders the use of such sheet material redundant for this purpose.

[0058] Typically, when two or more layers of cambered roof tiles are stacked with their orientations reversed in accordance with this further aspect of the invention, a tile in an upper layer will be supported on two adjacent tiles in the layer below. In particular, the upper tile will usually be supported at or adjacent to the extremities of its lowermost side edge on or close to the extremities of the uppermost side edge of a first underlying tile, and at or around the midpoint of its lowermost side edge on or close to the midpoint of the uppermost side edge of a second, adjacent underlying tile. In other words, the tiles in the upper layer (except perhaps the tiles at the end of each row) are generally supported at three contact points by the tiles below.

[0059] Whichever way the stacks are oriented, it is usually advisable for a group of tiles to be held together in the stack by means of a strap or band as otherwise the stack may collapse. Most commonly, the band or strap runs around the upper and lower edges of a group of tiles to avoid exerting a force on the interlocks. While the use of straps or bands remains advisable though not essential when the tiles are packed according to this further aspect of the invention, there is no need to interpose a sheet, such as of cardboard, between layers of tiles to prevent tiles in an upper layer from slipping down.

[0060] For most practical purposes, the base layer of tiles in the pack will be supported on a pallet allowing the pack to be readily transported for storage or use, and the pack may be covered in a protective wrapping, such as polythene sheet, in the normal way. The base layer may comprise more than one row of tiles, in which case it would be usual for each row to be overlaid with another row for most economical packing. Provided the tiles in an overlying row are oppositely facing to the tiles in the underlying row, it is not strictly necessary for all rows in a layer to face the same direction. However, it is more efficient to form the pack with all the tiles in one layer facing the same way.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order that the various aspects of the invention may be more readily understood, reference will now be made to the accompanying drawings, in which:

[0062]FIGS. 1a to 1 c and 2 to 5 are schematic diagrams illustrating flat roof tiles of known cross-sections that have been stacked in accordance with methods described above;

[0063]FIG. 6a is a perspective view from above of a tile according to an embodiment of one aspect of the present invention;

[0064]FIG. 6b is a perspective view from below of the tile in FIG. 6a;

[0065]FIG. 6c is a bottom plan view of the tile in FIG. 6a;

[0066]FIG. 6d is an end view taken from the upper edge of the tile of FIG. 6a;

[0067]FIG. 6e is a side view taken from the overlock side of the tile of FIG. 6a;

[0068]FIG. 6f is a top plan view of the tile of FIG. 6a;

[0069]FIG. 6g is an end view taken from the leading (lower) edge of the tile of FIG. 6a;

[0070]FIG. 6h is a side view taken from the underlock side of the tile of FIG. 6a;

[0071]FIG. 7 is a perspective view of a stack of four tiles each according to FIG. 6a;

[0072]FIG. 8 is an enlarged cross-section along line A-A of the stack of tiles shown in FIG. 7;

[0073]FIGS. 9a to 9 c are schematic diagrams showing a stack of tiles according to an embodiment of the same aspect of the present invention;

[0074]FIG. 10 is a perspective view of an array of tiles according to the same aspect of the invention as laid on a roof;

[0075]FIG. 11 is a perspective view of an array of tiles including a ventilation tile according to the same aspect of the invention as laid on a roof; and

[0076]FIG. 12 is a perspective view of a packing arrangement for cambered tiles in accordance with another aspect of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0077] Turning to FIG. 6a, there is shown an extruded tile (30) having a gently cambered upper surface (32). A pair of nail holes (34, 34′) extend through the tile between the upper surface (32) and the under surface (not visible). The tile (30) has a lower edge (36) which comprises the leading edge when the tile is laid on a roof. On its left side edge (38), the tile (30) is provided with an underlock (40). The underlock (40) does not extend as far as the leading edge (36) so that when the tiles are laid on a roof the underlock (40) is not visible.

[0078] The under surface (42) of the tile is shown in FIG. 6b. The underneath of the underlock (40) comprises an extension of the under surface (42) and, on the opposite right side edge (44), there is a corresponding overlock (46). Adjacent the upper edge (48) above the nail holes (34, 34′) there is a pair of hanging nibs (50, 50′). A pair of strengthening ribs (52, 52′) extend longitudinally on the under surface (42) roughly equidistant from each other and from the nearest side edge (38 or 44).

[0079] Each strengthening rib (52, 52′) has a region (54, 54′) spanning the mid-point of the unsupported length of the tile, the region being the deepest in cross-section of the entire tile. The regions (54, 54′) extend for almost half the length of the tile. The undersides of the regions (54, 54′) are slightly concave and have approximately the same radius of curvature as that of the upper surface (32) above the regions (54, 54′).

[0080] The under surface (42) is also provided adjacent the side edges, inwards of the underlock (40) and overlock (46), with a further pair of strengthening ribs (58, 58′) each of which includes an anti-rock bump (60, 60′) centrally disposed along the ribs (58, 58′). The depth of the tile at the anti-rock bumps (60, 60′) is less than the depth at the region (54, 54′), so that when an array of tiles (30) is packed, there is no frictional contact between the bumps (60, 60′) and the upper surface (32) of the adjacent underlying tile. The anti-rock bumps (60, 60′) inhibit any tendency for the tiles to rock relative to each other when the tiles are stacked and held together by a flexible strap (62) in the manner shown in FIG. 7.

[0081]FIGS. 6c to 6 h are variously plan, end and side views of the cambered roof tile shown in perspective in FIGS. 6a and 6 b. Owing to the fact that the tile illustrated is a cambered one, and that the difference in depth between the region of deepest cross-section (54, 54′) and the hanging nibs (50, 50′), although significant, is relatively small, the advantages of the invention are not readily apparent in these Figures.

[0082] However, FIG. 8, which represents an enlarged cross-section along line A-A of the stack of tiles shown in FIG. 7, clearly illustrates the creation of a slight gap between the tips of the hanging nibs (50, 50′) and the upper surface (32) of an underlying tile (30) when the tiles are laid on top of one another. By virtue of the regions of deepest cross-section (54, 54′) having a contour that is complementary to that of the cambered upper surface (32), the tiles are also stacked in parallel with each other providing a stable, flat-packed arrangement.

[0083]FIGS. 9a to 9 c are schematic diagrams illustrating the ability of the tiles according to the invention to be safely flat-packed with reduced risk of damage to their hanging nibs. In particular, FIG. 9a shows four such tiles (130) stacked vertically with their regions of deepest cross-section (154) resting against the upper surface (32) of an underlying tile and resulting in their respective hanging nibs (150) being held apart from said upper surface (132). When the stack of tiles (130) is turned through 90° to a vertical orientation (as shown in FIG. 9b), the integrity of the stack is generally maintained. However, if any slippage between tiles does occur, the regions of deepest cross-section substantially prevent the hanging nibs (150) from getting caught over the upper edges (148) of an adjacent tile (130). Consequently, any tiles that have slipped out of alignment can easily be brought back in line with the remaining tiles in the stack. Further, the upper edges (148) of the tiles (130) combine to present a substantially flat supporting surface on which a second vertical stack of tiles can be laid (as shown in FIG. 9c).

[0084]FIGS. 10 and 11 illustrate an array of roof tiles (30) in accordance with the invention as laid on a roof. The tiles are laid with their hanging nibs (not shown) suspended from wooden tile battens (66) and are fixed thereto by means of nails driven through their respective nail holes (34, 34′) in the conventional manner. A ventilation tile (68) is included in the array shown in FIG 11. The tiles (30, 68) provide the appearance of roof laid with conventional flat tiles, there being no visible evidence of the features characterising their under surface.

[0085]FIG. 12 illustrates a packing arrangement according to a further aspect of the invention in which tiles of the type illustrated in FIGS. 6a to 6 h are employed. In particular, it shows a first layer (70) of cambered, interlocking tiles (30) in the form of two rows (72, 72′) of tiles (30) laid side by side is overlaid with a second layer (74) of the same tiles (30) also in two rows (76, 76′) laid side by side. The tiles (30) in the first layer (70) are stacked together vertically each resting on their respective side edges (44) comprised of the overlock (46). The opposite side edges (38) comprised of the underlock (40) combine to form the supporting “surface” on which the second layer (74) of tiles (30) is laid.

[0086] The tiles (30) of the first layer (70) are all laid facing in the same direction, namely with their gently cambered upper surface (32) facing forwards, and the tiles (30) of the second layer (74) are also laid facing in the same direction as other tiles in the second layer, but with their under surface (42) facing forwards. Essentially, the tiles (30) in the upper layer (74) are turned through 180° with respect to the tiles (30) in the first, base layer (70). Each tile (30) in the second layer (74) contacts two adjacent, underlying tiles (30) in the first layer (70). Specifically, the overlock (46) of each tile in the upper layer (74) contacts the underlock (40) of one underlying tile adjacent their respective upper and lower edges (48, 36) and of an adjacent underlying tile at their respective mid-points (78).

[0087] By virtue of their relative orientations, the gaps (80) created between the respective underlocks (40) in adjacent tiles (30) in the first layer (70) are curved in the opposite direction to the camber of the overlocks (46) of the tiles (30) of the second layer (74) such that the latter are unable to fall down into the gaps (80).

[0088] Other variations are possible within the inventive concept of the invention in its various aspects, and the present invention may be embodied in other specific forms without departing from its essential attributes. Accordingly, reference should be made to the appended claims and other conceptual statements herein rather than the foregoing specific description as indicating the scope of the invention. 

1. A flat roof tile comprising an upper edge, a lower edge, two oppositely facing side edges, an upper surface and an under surface provided with at least one hanging nib, wherein the under surface includes at least one region spaced from the or each hanging nib where the tile is deeper in cross-section than any other part of the tile and the underside of the or each region is configured so that when the tile is superposed on a second said tile, the tiles lie parallel and the underside lies in substantial contact with the upper surface of the second tile and prevents the hanging nib(s) of the first tile from contacting the upper surface of the second tile.
 2. A roof tile according to claim 1, wherein the underside of the region of deepest cross-section has a contour that is complementary to the contour of upper surface above the region.
 3. A roof tile according to claim 1, wherein the or each region encompasses or spans the middle portion of the under surface.
 4. A roof tile according to claim 1, wherein the or each region is located symmetrically around the mid-point of the tile's unsupported span in use.
 5. A roof tile according to claim 1, wherein the region of deepest cross-section does not extend into the area of the under surface that overlaps in use with the upper surface of an underlying tile in an adjacent row.
 6. A roof tile according to claim 4, wherein the or each region extends for between about one third to two thirds of the length or width of the tile or both.
 7. A roof tile according to claim 1, wherein the under surface of the tile tapers from the boundary of the region's underside in the direction of the tile edges.
 8. A roof tile according to claim 1, wherein the tile is provided with a plurality of ribs on its under surface at least one such rib including along a mid-portion the region of deepest cross-section.
 9. A roof tile according to claim 8, wherein a pair of ribs are symmetrically disposed on either side of the mid-point of the unsupported tile span in use and extend longitudinally between the upper edge and the lower edge but not to the said edges.
 10. A roof tile according to claim 9, wherein the pair of ribs are spaced equidistant from each other and from the side edges of the tile.
 11. A roof tile according to claim 1, wherein the or each region of deepest cross-section has a depth that is sufficient to avoid frictional contact between the hanging nib(s) and the upper surface of another such tile when the tiles are superposed.
 12. A roof tile according to claim 11, wherein the depth of the tile at the region is 0.1 mm or more greater than the depth at the hanging nib(s).
 13. A roof tile according to claim 12, wherein the depth of the tile at the region is 0.5 mm greater than the depth at the hanging nib(s).
 14. A roof tile according to claim 1, wherein the tile has a planar upper surface and the underside of the or each region is planar.
 15. A roof tile according to claim 1, wherein the tile has a cambered upper surface and the underside of the or each region is concave having a degree of curvature complementary to the camber.
 16. A roof tile according to claim 1, wherein the tile is made of concrete.
 17. A roof tile according to claim 1, wherein the tile is made by extrusion.
 18. A roof tile having a substantially planar upper surface and an under surface from which one or more hanging nibs depend, characterised in that the under surface is provided with one or more elongate ribs each having a median portion that depends beyond the depth of the hanging nib(s) and its underside is of complementary configuration to the upper surface lying immediately thereabove.
 19. An array of tiles fixed to a supporting surface, the array including a plurality of tiles according to claim
 1. 20. A roof structure comprising a plurality of roof tiles according to claim 1, said tiles being laid in side-by-side and overlapping lower edge-over-upper edge relationship on a support structure to form a roof.
 21. A roof structure according to claim 20, further including one or more ventilation tiles adapted to co-operate with adjacent roof tiles in the same row in side-by-side interlocking relationship and with roof tiles in an adjacent row in upper edge-to-lower edge overlapping relationship.
 22. A method of forming a pack of cambered roof tiles including: stacking together a first group of said tiles so that each tile in the group is supported on a side edge with their respective upper and lower edges parallel and vertically aligned to form a first layer of said tiles; and stacking together a second group of said tiles on top of said first group, the tiles in said second group also supported on a side edge with their respective upper and lower edges being parallel and vertically aligned to form a second layer of said tiles; wherein prior to stacking on the first group, the tiles of the second group are turned through 180° to face the opposite direction to those of the first group.
 23. The method of claim 22, wherein the roof tiles are interlocking roof tiles.
 24. The method of claim 22, wherein a roof tile in an upper layer is supported on two adjacent roof tiles in the layer beneath.
 25. The method of claim 22, wherein said roof tiles comprise tiles according to claim
 1. 26. A pack of cambered roof tiles comprising first and second layers of tiles, the tiles in each layer stacked together and supported on their side edges with their respective upper and lower edges parallel and vertically aligned, wherein the orientation of the tiles in the second layer is reversed such that they face the opposite direction to the tiles of the first layer.
 27. The pack of claim 26, wherein the roof tiles are interlocking roof tiles.
 28. The pack of claim 26, wherein a roof tile in an upper layer is supported on two adjacent roof tiles in the layer beneath.
 29. The pack of claim 26, wherein said roof tiles comprise tiles comprising an upper edge, a lower edge, two oppositely facing side edges, an upper surface and an under surface provided with at least one hanging nib, wherein the under surface includes at least one region spaced from the or each hanging nib where the tile is deeper in cross-section than any other part of the tile and the underside of the or each region is configured so that when the tile is superposed on a second said tile, the tiles lie parallel and the underside lies in substantial contact with the upper surface of the second tile and prevents the hanging nib(s) of the first tile from contacting the upper surface of the second tile.. 